Production of titanium sesquioxide



i j v Patented June 22, 1954 PRODUCTION OF TITANIUM SESQUIOXIDE Merle E. Sibert, Garfield Heights, and Stuart S.

Carlton, Parma, Ohio, assignor s, by mesne assignments, to Horizons Titanium Corporation, Princeton, N. J a corporation of New Jersey No Drawing. Application May 24, 1952, Serial No. 289,879

8 Claims.

This invention relates to the production of titanium sesquioxide and, more particularly, to a method of producing titanium sesquioxide sub stantially uncontaminated by other oxides of titanium.

There has been described and used heretofore a method of producing titanium monoxide by heating an intimate mixture of titanium carbide and a metal oxide such as zinc oxide, magnesia or lime to a temperature within the range of 1300 to 1750" C. In the course of an investigation of the chemistry and mechanism of this reaction, we have discovered that the titanium monoxide is formed by two successive reaction stages, the first stage being the conversion of titanium carbide to titanium sesquioxide and the second stage comprising the conversion of the titanium sesquioxide to titanium monoxide. Although our investigation showed that the two reaction stages take place simultaneously throughout the reaction mass at temperatures within the range of 1300 to 1750* C., and that titanium sesquioxide is formed simultaneously with titanium monoxide Within the reaction mass, we have discovered that the first reaction can be made to proceed to the substantial exclusion of the second reaction provided a lower temperature range is used than that heretofore required in the aforementioned method of producing titanium monoxide. Thus, we have found that if a mixture of the titanium carbide and metal oxide is heated to a temperature within the range of 1000" to 1200 C. in an inert atmosphere, substantially pure titanium sesquioxide is produced. When this titanium sesquioxide is subsequently reacted with a further quantity of titanium carbide, the resulting titanium monoxide is less contaminated with higher oxides of titanium than when the monoxide is produced in the aforementioned single stage process.

Accordingly, our novel method of producing titanium sesquioxide comprises forming an intimate mixture of finely divided titanium carbide and a readily reducible metal oxide the metal component of which is volatile at a temperature of 1000 to 1200 C., the amount of titanium carbide being at least stoichiometrically equivalent to that of the metal oxide, heating the mixture to a temperature within the range of about l000 to 1200 C. in an inert atmosphere, removing the resulting evolved carbon monoxide and vapors of the metal component of said metal oxide, and recovering the resulting residual titanium sesquioxide.

The titanium carbide which is used in practicing the method of our invention should be substantially pure in order to avoid contamination of the titanium sesquioxide with the impurities otherwise associated with the titanium carbide. The impurities normally present in significant amounts in titanium carbide of commercial grade comprise iron and graphite. The iron can be effectively removed by grinding the titanium carbide to a particle size of minus 325 mesh (Tyler standard), and preferably to a particle size of about one micron or smaller, adding hydrochloric acid to an aqueous slurry of the finely ground carbide, and subsequently washing the carbide to remove entrained chlorides. The removal of graphite from the titanium carbide is not essential if the titanium sesquioxide produced therefrom is to be reacted with a further quantity of titanium carbide for the production of titanium monoxide, but the graphite may be an undesirable impurity if carried over to the titanium sesquioxide to be used for other purposes. If the graphite need be removed, this can be effected by dispersing the titanium carbide in a slightly alkaline aqueous medium and separating the graphite by conventional froth flotation procedure. Inasmuch as the treatment of commercial grade titanium carbide for the removal of contaminated iron is generally resorted to, the resulting finely divided form of the purified titanium carbide is advantageous because it enhances its reactivity with the metal oxide.

The metal oxides which may be reacted with titanium carbide in the practice of our invention comprise those metal oxides which are not only reducible at temperatures of about 1000 to 1200 C. but are further characterized by volatilization of the metal component of the oxide within this temperature range. Zinc oxide, magnesium oxide and calcium oxide are illustrative of such metal oxides, the zinc oxide and magnesium oxide being particularly effective. For maximum reactivity with the titanium carbide, the metal oxide admixed therewith should also be in finely divided form, and in general it can be said that those metal oxides which are suitable for the practice of our invention are readilyavallable in commercial quantities in such finely divided form as to be adapted for admixture with the titanium carbide without further treatment to reduce their particle size.

The admixture of the titanium carbide and the metal oxide is preferably carried out with sufficient thoroughness to insure uniform distribution of both components throughout the mixture. Al+

though intimacy of contact between the reactants is provided by such thorough mixing, we have found it to be further advisable to enhance the intimate contact of the titanium carbide and metal oxide particles by compressing the mixture. For example, we have obtained particularly effective results by adding about 5 to by weight of water as a temporary binder for the mixture and by subsequently pelletizing the damp mixture under compressive pressures of 10 tons per square inch and higher. The resulting intimate contact is, we have found, conducive to substantially quantitative reaction between the titanium carbide and the metal oxide.

Inasmuch as, in our process, the titanium carbide and metal oxide react substantially quantitatively in a manner which can be expressed by the equation 2TiC+5MgO- Ti2O3+5Mg+2CO, the relative amounts of the reactants can be definitely specified. Thus, in order that the titanium sesquioXide be substantially free of contamination by unreacted metal oxide, the mixture should be composed of an amount of the titanium carbide at least stoichiometrically equivalent to that of the metal oxide. If the titanium sesquioxide is to be used for such purpose as, for example, a starting material in the production of other trivalent titanium compounds, it is generally advisable to use substantially stoichiometric quantities of the titanium carbide and metal oxide so that the final product will be composed substantially exclusively of titanium sesquioxide. On the other hand, if the titanium sesquioxide is to be reacted with a further quantity of titanium carbide for the production of titanium monoxide,

a portion or all of this further quantity of titanium carbide may be incorporated in the initial titanium carbide-metal oxide mixture. The aforementoned variation in the relative amounts of titanium carbide and metal oxide which may be used in practicing our invention appears to have no significant effect upon the reactivity of the mixture at temperatures within the range which we have found to be important.

The temperatures which we have found to be conducive to the formation of titanium sesquioxide substantially uncontaminated by other titanium oxides pursuant to our invention lie within the range of about l000 to about 1200 C. Within this range, higher temperatures make possible the use of shorter reaction periods, but within the entire temperature range we have found that substantially complete conversion of the titanium carbide to titanium sesquioxide is effected within a maximum of about three hours. A reaction period of one to two hours is generally sufficient for complete reaction at temperatures approximating the upper limit of the useful temperature range. In any event, the proper duration of the reaction period may be ascertained by cessation of evolution of the gaseous reaction products.

Under the aforementioned reaction conditions, the gaseous reaction products comprise carbon monoxide and the vapor of the metal component of the metal oxide and the residual reaction product comprises titanium sesquioxide. The removal of the carbon monoxide and metal vapor from the reaction zone, and hence the progress of the reaction, are enhanced by the two procedures which we have found to be particularly useful in maintaining the desired inert atmosphere in the reaction zone. Thus, we have found it to be advisable either to sweep the reaction zone with a stream of inert gas or preferably to maintain active vacuum pumping conditions throughout the reaction period. Argon and helium are typical of useful inert gases, and vacuums of the order of 10 millimeters of mercury or less are generally suitable for the practice of our invention, although we prefer to maintain vacuums of the order of 50 to 100 microns of mercury. Both procedures for the maintenance of a substantially inert reaction atmosphere remove the carbon monoxide and metal vapor as rapidly as they are evolved, and the mixture of gases is one from which the metal vapor can be condensed to a substantially unoxidized and useful form with conventional condensation apparatus.

The reaction vessel used in practicing our invention should, of course, be such as to prevent contamination of the reaction product. For example, molybdenum and Hastaloy may be used satisfactorily for the vessel which holds the reaction mass, and conventional furnace refractories may be used for those parts of the heating apparatus which are exposed merely to the gaseous products of the reaction. Thus, we have found that a molybdenum-lined graphite crucible positioned within an electrically heated furnace is particularly satisfactory equipment for either small or large scale operation.

The practice of our invention is illustrated by the following specific examples.

Example I A mixture composed of 60.4 parts of titanium carbide (freed of contaminating iron as described hereinbefore but containing 0.8% free graphitic carbon) ground to a particle size of about one micron and 166.6 parts by weight of pigment grade zinc oxide (having a 0.5% by weight ignition loss) was moistened with water and was then pelleted under a pressure of about 10 tons per square inch. The pellets were charged to a molybdenum-lined crucible placed within an induction-heated vacuum furnace. A starting vacuum of about 50 to 60 microns was established and. maintained by active pumping throughout the entire reaction period. The pellets were heated for 150 minutes at a temperature of about 1200 0., carbon monoxide and metallic zinc vapor being the sole gaseous products evolved and metallic zinc being condensed from the gaseous mixture. After cooling the furnace, the residue in the crucible was ascertained by X-ray analysis to be composed of titanium sesquioxide (TizOs) with a minute amount of titanium monoxide (TiO) in solid solution in a small amount of unreacted titanium carbide.

Example II A mixture composed of 24 parts of pure titanium carbide and 40 parts by weight of electrically fused periclase (MgO), both components having been ground to a particle size of minus 325 mesh (Tyler standard), was moistened with water and pelletized. The pellets were heated in a molybdenum-lined graphite crucible in an electrically heated vacuum furnace for a period of about minutes at a temperature of about 1200" C. while maintaining a vacuum between 50 and microns of mercury. A mixture of carbon monoxide and metallic magnesium vapor was evolved and the metallic magnesium was condensed therefrom. Chemical and X-ray analyses of the black residue obtained after cooling the furnace while maintaining the aforesaid vacuum conditions established that the residue was substantially pure titanium sesquioxide (T1203).

It will be seen, accordingly, that the method 01" our invention is capable of producing titanium sesquioxide substantially uncontaminated by other compounds, particularly by other titanium oxides. Consequently, our method may be used advantageously in conjunction with various processes for producing other titanium compounds of high purity, one such process comprising the use of titanium sesquioxide for conversion of titanium carbide to titanium monoxide and the use of the latter as a starting material from which titanium metal may be produced by fused bath electrolysis. Accordingly, the expression recovering the residual titanium sesquioxide, as used herein and in the claims, includes recovering the sesquioxide as such as Well as recovering it at a reactant which, in admixture with residual or extraneous titanium carbide, is converted to titanium monoxide in a subsequent heating operation carried out at a temperature substantially in excess of that used in producing the sesquioxide by the method of our invention.

We claim:

1. The method of producing titanium sesquioxide which comprises forming an intimate mixture of finely divided titanium carbide and a metal oxide of the group consisting of magnesium oxide, zinc oxide and calcium oxide, the amount of titanium carbide being at least stoichiometrically equivalent to that of the metal oxide, heating the mixture to a temperature within the range of about 1080" to 1200 C. in an inert atmosphere, removing the resulting evolved carbon monoxide and vapors of the metal component of said metal oxide, and recovering the resulting residual titanium sesquioxide product.

2. The method of producing titanium sesquioxide which comprises forming an intimate mixture of finely divided titanium carbide and a metal oxide of the group consisting of magnesium oxide, zinc oxide and calcium oxide, the amount of titanium carbide being at least stoichiometrically equivalent to that of the metal oxide, heating the mixture to a temperature within the range of about 1000 to 1200 C. in an inert atmosphere for a period of time sufficient to volatilize and drive off substantially all of the metal component of said metal oxide, removing the resulting evolved carbon monoxide and vapors of the metal of said metal oxide, and recovering the resulting residual titanium sesquioxide product.

3. The method of producing titanium sesquioxide which comprises forming an intimate mixture of finely divided titanium carbide and magnesium oxide, the amount of titanium carbide being at least stoichiometrically equivalent to that of the magnesium oxide, heating the mixture to a temperature within the range of about 1000 to 1200 C. in an inert atmosphere, removing the resulting evolved carbon monoxide and vapors of the magnesium component of said magnesium oxide, and recovering the resulting residual titanium sesquioxide product.

4. The method of producing titanium sesquioxide which comprises forming an intimate mixture of finely divided titanium carbide and zinc oxide, the amount of titanium carbide being at least stoichiometrically equivalent to that of the zinc oxide, heating the mixture to a temperature within the range of about 1000 to 1200 C. in an inert atmosphere, removing the resulting evolved carbon monoxide and vapors of the zinc component of said zinc oxide, and recovering the resulting residual titanium sesquioxide product.

5. The method of producing a titanium sesquioxide product which comprises forming an intimate mixture of finely divided titanium carbide and a metal oxide of the group consisting of magnesium oxide, zinc oxide and calcium oxide, the amount of titanium carbide being stoichiometrically in excess of that of the metal oxide, heating the mixture to a temperature within the range of about 1.000" to 1200 C. in an inert atmosphere, removing the resulting evolved carbon monoxide and vapors of the metal of said metal oxide, and recovering the resulting residual product composed essentially of titanium sesquioxide and unreacted titanium carbide.

6. The method of producing titanium sesquioxide which comprises forming an intimate mixture of stoichiometric amounts of finely divided titanium carbide and a metal oxide of the group consisting of magnesium oxide, zinc oxide and calcium oxide, heating the mixture to a temperature within the range of about 1000 to 1200" C. in an inert atmosphere, removing the resulting evolved carbon monoxide and vapors of the metal component of said metal oxide, and recovering the resulting residual titanium sesquioxide product.

7. The method of producing titanium sesquioxide which comprises forming a pelleted intimate mixture of finely divided titanium carbide and a metal oxide of the group consisting of magnesium oxide, zinc oxide and calcium oxide, the amount of titanium carbide being at least stoichiometrically equivalent to that of the metal oxide, heating the mixture to a temperature within the range of about 1000 to 1200 C. in an inert atmosphere for a period of time sufilcient to volatilize and drive off substantially all of the metal component of said metal oxide, removing the resulting evolved carbon monoxide and vapors of the metal of said metal oxide, and recovering the resulting residual titanium sesquioxide product.

8. The method of producing a titanium sesquioxide product which comprises forming an intimate mixture of finely divided titanium carbide and a metal oxide of the group consisting of magnesium oxide, zinc oxide and calcium oxide, the amount of titanium carbide being stoichiometrically in excess of that of the metal oxide, heating the mixture to a temperature within the range of about 1000 to 1200 C. in a vacuum of about 50 to microns of mercury, removing the resulting evolved carbon monoxide and. vapors of the metal of said metal oxide, and recovering the resulting residual product composed essentially of titanium sesquioxide and unreacted titanium carbide.

No references cited. 

1. THE METHOD OF PRODUCING TITANIUM SESQUIOXIDE WHICH COMPRISES FORMING AN INTIMATE MIXTURE OF FINELY DIVIDED TITANIUM CARBIDE AND A METAL OXIDE OF THE GROUP CONSISTING OF MAGNESIUM OXIDE, ZINC OXIDE AND CALCIUM OXIDE, THE AMOUNT OF TITANIUM CARBIDE BEING AT LEAST STOICHIOMETRICALLY EQUIVALENT TO THAT OF THE METAL OXIDE, HEATING THE MIXTURE TO A TEMPERATURE WITHIN THE RANGE OF ABOUT 1000* TO 1200* C. IN AN INERT ATMOSPHERE, REMOVING THE RESULTING EVOLVED CARBON MONOXIDE AND VAPORS OF THE METAL COMPONENT OF SAID METAL OXIDE, AND RECOVERING THE RESULTING RESIDUAL TITANIUM SESQUIOXIDE PRODUCT. 